In the following, the invention will be described on the basis of a refrigerant compressor, for example as used in domestic refrigerators and freezers. Such a compressor should work in a substantially maintenance-free manner and still have a good efficiency.
This requires the lowest possible friction between the mechanical components of the compressor. In this connection, the friction is not only influenced by the relative movement of the sliding and rotating components, but also by jamming effects occurring from the sum of shape and position deviations.
A sufficient tightness when the piston moves in the cylinder, for example, requires a very accurate adaptation of the piston to the cylinder. Further, the piston must move as exactly as possible along the axis of the cylinder. As soon as an angle error occurs, the piston moves in the cylinder in an unbalanced manner, so that increased friction and increased wear occur. Finally, leakages may occur in the compressor, which will further reduce the efficiency.
A substantial reason for the occurrence of such angle errors is the lack of parallelism between the two connecting rod eyes of the connecting rod. With the manufacturing methods used until now, it has not been possible to obtain an axis parallelism of 2 μm or less in relation to a length of 20 mm. Previously, a relatively expensive subsequent mechanical treatment would be required to obtain a higher accuracy. However, this subsequent mechanical treatment will change the tribologic properties of the connecting rod arrangement, in particular the wear resistance.
DE 10 2006 028 617 B3 discloses a connecting rod arrangement that has a rotating joint between the crank eye and the connecting rod eye. This rotating joint permits a slewing movement of the crank eye in relation to the connecting rod eye, so that angle errors are equalised. However, the manufacturing of such a connecting rod arrangement is relatively expensive. The additional bearing causes the connecting rod arrangement to have a relatively large weight, which is disadvantageous with regard to heavy vibrations. The bearing may also permit a play between the connecting rod eye and the crank eye, which further deteriorates the efficiency.